The present invention relates to a scroll compressor which is employed as a coolant compressor, and more particularly to a scroll compressor having improvements in the pathways for gas sucked through the compressor.
Prior to describing the invention, the principles of a conventional scroll compressor will be described.
The fundamental components of a conventional scroll compressor are shown in FIGS. 1A through 1D. In these figures, reference numeral 1 designates a stationary scroll, 2 an orbiting scroll, 5 a compression chamber formed by the scrolls 1 and 2, and 0, the center of the stationary scroll.
The stationary scroll 1 and the orbiting scroll 2 are a pair of spiral-shaped wraps which have the same configuration but are wound in opposite directions. The spiral structures are involute or arcuate in section. The spiral structures are combined together to form the compression chamber 5 therebetween.
The operation of the scroll compressor will now be described. As shown in FIGS. 1A through 1D, the orbiting scroll 2 moves around the center 0 of the stationary scroll 1, that is, it orbits about the center 0 with its angular orientation relative to a stationary reference unchanged, that is, without rotational movement. Due to this movement of the orbiting scroll 2, the volume of the compression chamber 5 is periodically decreased, as a result of which gas taken into the compression chamber 5 is compressed and discharged.
An example of a conventional scroll compressor will be described with reference to FIG. 2. The scroll compressor shown in FIG. 2 is intended to be applied to a refrigerator, an air conditioner or an air compressor, for instance, where it is used to compress a refrigerant gas such as Freon.TM.. In FIG. 2, reference numeral 1 designates a stationary scroll, 2 an orbiting scroll, 3 the base plate of the orbiting scroll 2, with the base plate having a diametrical groove 3A on the back thereof, 4 an orbiting scroll shaft, 5 a compression chamber, 6 the suction inlet of the compression chamber 5, 7 a ring slightly spaced apart from the back of the orbiting scroll base plate 3, 8 a ring-shaped Oldham coupling for preventing rotation of the orbiting scroll 2 while permitting the latter to orbit, with the coupling 8 having protrusions 8a and 8b arranged crosswise, 9 a thrust bearing supporting the back of the orbiting scroll base plate 3, 10 a frame or a bearing support to which is fixed the stationary scroll 1 with screws and which is secured to a shell (described below) by press fitting, 11 an Oldham chamber formed between the base plate 3 and the ring 7 and the bearing support 10, 12 oil returning holes formed in the bearing support 10, through which the Oldham chamber is communicated with a motor chamber (described below), 13 an electric motor, 13a a motor stator, and 13b a motor rotor.
Further in FIG. 2, reference numeral 14 designates a crankshaft, 15 oil holes formed eccentrically in the crankshaft 14, 16 an orbiting bearing formed eccentrically on the crankshaft 14 and engaged with the orbiting scroll shaft 4, 17 a main bearing engaged with the upper portion of the crankshaft 14, 18 a motor bearing engaged with the middle portion of the crankshaft 14, 19 a motor chamber formed by the bearing suppport 10, the motor stator 13a and the motor rotor 13b, 20 a first balancer secured to the upper portion of the motor rotor 13b, 21 a second balancer secured to the lower portion of the motor rotor 13b, 22 a shell which fixes the bearing support 10 and seals the entire compressor, 23 an oil pool formed on the bottom of the shell 22, 24 a suction pipe through which the motor chamber 19 is communicated with the outside, 25 an air gap between the motor stator 13a and the motor rotor 13b, 26 flow paths formed between the outer wall of the bearing support 10 and the inner wall of the shell 22 having lower ends opening above the oil pool 23 in the shell 22 and upper ends communicating with the suction chamber 6, 27 a discharge pile for discharging gas from the central portion of the stationary scroll to the outside of the shell 22, and 28 throughholes in the motor rotor 13b.
The operation of the scroll compressor thus constructed will be described.
When current is applied to the motor stator 13a, the motor stator 13b generates torque to drive the crankshaft 14. When the crankshaft 14 starts rotating, its torque is transmitted to the orbiting scroll shaft 4 engaged with the orbiting bearing which is formed eccentrically on the crankshaft 14 so that the orbiting scroll 2 is orbited while being guided by the Oldham coupling 8, thus performing a compression action as depicted in FIG. 1. The flow of gas is as indicated by the solid line arrow. The gas which enters the motor chamber 19 through the suction pipe 24 cools the motor stator 13a and the motor rotor 13b while passing through the air gap 25 and the ventilating holes 28. Then, the direction of flow of the gas is changed above the oil pool 23. The gas is pulled into the suction chamber 6 after passing through the flow path 26 and is then introduced into the compression chamber 5. As the crankshaft 14 rotates, the gas is delivered towards the center of the compressor and is then discharged through the discharge pipe provided at the center of the stationary scroll 1.
Next, the lubricating system of the compressor will be described. The lubricant in the oil pool 23 is sucked upwardly through the lower end of the crankshaft 14 by the pumping action of the oil holes 15 formed eccentrically in the crankshaft 14 as indicated by the broken line arrows in FIG. 2. The lubricant is thus supplied through the oil holes 15 to the orbiting bearing 16, the main bearing 17, the motor bearing 18, and the thrust bearing 9, and is then delivered into the Oldhams chamber 11. The lubricant pooled in the Oldhams chamber 11 is dropped into the motor chamber 19 through the oil returning holes 12 and returned to the oil pool 23 through the air gap 25.
The orbital motion of the orbiting scroll 2 caused by the rotation of the crankshaft 14 tends to cause the whole compressor to vibrate. However, as balance around the crankshaft 14 is maintained by the first and second balancers 20 and 21, the compressor operates without abnormal vibration.
In the conventional scroll compressor thus constructed, the gas sucked into the motor chamber 19 through the suction pipe 24 flows above the oil pool after passing through the air gap 25 and the ventilating holes 28, striking the lubricant in the oil pool 23 and then reversing its direction of flow. Then, after passing through the flow paths 26, the gas is sucked into the suction chamber 6. The lubricant in the oil pool 23 is agitated by the rotation of crankshaft 14 at all times. Therefore, the surface of the lubricant is not still as shown in FIG. 2, that is, it tends to rotate in the oil pool and be splashed thereabout. As the air gap 25 and the ventilating holes 28 have a relatively small cross-sectional area, the gas increases in speed when passing therethrough, thus striking the lubricant in the oil pool 23. When striking the lubricant, the gas imparts its force to the lubricant so that the latter is splashed. The splashed droplets, carried by the sucked gas, pass through the flow paths 26, and are sucked into the suction chamber 6. When the compressor is stopped, coolant tends to be mixed into the oil in the oil pool 23. When the compressor is started, the abrupt pressure decrease causes foaming of the lubricant. If excessive lubricant is present, the amount of lubricant in the oil pool 23 will be gradually depleted because the lubricant is discharged out of the compressor through the discharge pipe 27. The amount of lubricant supplied through the oil holes 16 to the bearings may become insufficient, making it impossible to operate the compressor safely.
In general, a motor generates heat when operated. The conventional scroll compressor is so designed that the intake gas absorbs the heat thus generated when passing through the air gap 25 and the ventilating holes 28 and when flowing along the outer wall of the motor stator 13a and passing through the flow paths 26. Accordingly, the motor is sufficiently cooled. However, as the gas absorbs the heat generated by the motor, the temperature of the gas is high, as a result of which the gas has a small specific gravity, that is, the gas is thin at the point where it enters the suction chamber 6. When such thin gas is sucked into the compression chamber 5 from the suction chamber 6, the mass of intake gas per revolution of the crankshaft 14 is small, as a result of which the efficiency of the compressor is low. Furthermore, since the ventilating holes 28 of the motor rotor 13b and the air gap 25 are generally considerably small in cross-sectional area, a pressure loss is caused when the gas passes therethrough, which adversely affects the performance of the compressor.
Accordingly, an object of the invention is to eliminate the above-described difficulties accompanying a conventional scroll compressor.